The present invention relates to a network technique and more particularly, to a method for allocating a subchannel in a wireless network.
In a multi-user wireless network, its important challenge is how a base station allocates channels to a plurality of users. First consider conventional scheduling specifications in a wireless network having a plurality of users for a single channel. In general, user channels have different statistical characteristics. Thus, when a channel is allocated always to a user having a highest quality of communication even in a small area according to the scheduling specifications, a system throughput is increased but this is unfair to a user in deep fading. In order to solve the above weak point, proportional fairness scheduling specifications as a compromise among diversity gain, fairness, and system throughput, has been proposed. For the proportional fairness scheduling specifications, refer to P. Viswaanath. David N. Tse and R. Laroia “Opportunistic beamforming using dumb antennas” IEEE Transactions On Information Theory, Vol. 48, June 2002, pp. 1277-1294.
Assume that there is a feedback channel having no error from each user to a base station. Also assume that data transmission rates of a channel currently supportable by N users are denoted by R1(n), R2(n), . . . , and RN(n), and that average throughputs in a time slot slide window tc at a time n are denoted by T1(n), T2(n), . . . , and TN(n). Under this proportional fairness scheduling specifications, the base station transmits data to a user having a maximum proportional value of an equation (1) given below.
                                          R            k                    ⁡                      (            n            )                                                T            k                    ⁡                      (            n            )                                              (        1        )            
In this case, the proportional value shown by the above equation (1) is directly proportional to the data transmission rate and the channel gain supported by a forward link, and is inversely proportional to an average throughput. Thus, when a proportion of user's momentary channel quality to average channel conditions at a time slot tc is great, the user in question is selected for transmission according to the scheduling specifications. In other words, the competition of users' resources, i.e., channels is carried out on the basis of not the data transmission rate supported directly by the user but the proportional value normalized using each own average throughput.